NEFL and proximal spinal muscular atrophy: Table 2 demonstrates that NfL and pNfH were used as potential pharmacodynamic (response) biomarkers in the majority of studies that examined the utility of molecular biomarkers for monitoring therapeutic response in SMA. In the majority of studies, a decrease in NfL and pNfH levels was observed following treatment with nusinersen [39,61,62,63,76,77,78,79,80,81], whereas others observed no change in the levels of these biomarkers [45,56,60,82,83,84] (Table 2).